This invention relates to a new medical use for a group of heterocyclic compounds and pharmaceutical compositions containing them. In particular it relates to certain tetrahydrocarbazolone derivatives which may be used to promote gastric emptying and as anti-emetic agents.
A particularly important application for anti-emetic agents is in the prevention and treatment of nausea and vomiting associated with cancer chemotherapy. Emesis is a well-known and frequent side-effect of cancer chemotherapeutic agents, such as cisplatin. It causes serious problems in cancer chemotherapy, and in some patients emesis is so severe that therapy must be discontinued. Anti-emetic agents are therefore often administered in order to alleviate this side-effect of the cancer chemotherapeutic agent. The anti-emetic agents employed are usually benzamide derivatives, such as metoclopramide, which have dopamine antagonist activity.
Metoclopramide is also a gastric motility stimulant, i.e. it promotes gastric emptying. The promotion of gastric emptying is important in the treatment of gastro-intestinal disorders related to gastric stasis; and in radiological examinations.
In view of their dopamine antagonist activity benzamide derivatives such as metoclopramide themselves exhibit serious and undesirable side-effects, such as extra-pyramidal effects, i.e. tardive dyskinesia, acute distonia, akathisia and tremor. There is thus a need for a safe and effective anti-emetic agent and gastric motility stimulant.
In our British patent application No. 2153821A and our European patent application No. 86300423 we disclose 3-imidazolylmethyltetrahydrocarbazolones which may be represented by the general formula (I) 
wherein
R1 represents a hydrogen atom or a C1-10 alkyl, C3-7 cycloalkyl, C3-7cycloalkyl-(C1-4)alkyl, C3-6 alkenyl, C3-10 alkynyl, phenyl or phenyl-C1-3alkyl group, and one of the groups represented by R2, R3 and R4 is a hydrogen atom or a C1-6 alkyl, C3-7 cycloalkyl, C2-6 alkenyl or phenyl-C1-3alkyl group and each of the other two groups, which may be the same or different, represents a hydrogen atom or a C1-6 alkyl group; and physiologically acceptable salts and solvates, e.g. hydrates, thereof.
Suitable physiologically acceptable salts of the carbazolones of general formula (I) include acid addition salts formed with organic or inorganic acids for example, hydrochlorides, hydrobromides, sulphates, phosphates, citrates, fumarates and maleates. The solvates may, for example, be hydrates.
The aforementioned specifications also disclose physiologically acceptable equivalents of the compounds of formula (I), i.e. physiologically acceptable compounds which are converted in vivo into the parent compound of formula (I).
The compounds of formula (I) are described in the aforementioned specifications as potent and selective antagonists of 5-hydroxytryptamine (5-HT) at xe2x80x98neuronalxe2x80x99 5-HT receptors of the type located on terminals of primary afferent nerves, and which are also believed to be present in the central nervous system. The compounds are described as being of use in the treatment of a human or animal subject suffering from a condition caused by a disturbance of neuronal 5HT function, for example in the treatment of a human subject suffering from migraine pain or a psychotic disorder such as schizophrenia. It is also stated that the compounds may be useful in the treatment of conditions such as anxiety, obesity and mania.
We have now surprisingly found that compounds of formula (I) promote gastric emptying and also that they are anti-emetic.
Accordingly, the invention provides a method of treatment for the relief of nausea and vomiting, and/or the promotion of gastric emptying e.g. for the relief of gastro-intestinal disorders associated with gastric stasis, which comprises administering to a human or animal subject an effective amount of a compound of formula (I), or a physiologically acceptable salt or solvate thereof.
Tests in animals have shown that compounds of formula (I) enhance gastric emptying. The compounds are therefore of use in the treatment and/or prevention of conditions which may be relieved by the promotion of gastric emptying e.g. gastric stasis which may occur, for example, post-operatively, and symptoms of gastro-intestinal dysfunction such as occur with dyspepsia, peptic ulcer, reflux oesophagitis and flatulence. The compounds may also be used to promote gastric emptying in diagnostic radiological procedures, such as radiological examinations.
Tests in animals have also shown that compounds of formula (I) inhibit emesis. The compounds are therefore also of use as anti-emetic agents, i.e. in the prevention and treatment of nausea and vomiting. The compounds are especially valuable for the prevention of emesis induced by cancer chemotherapeutic agents such as cisplatin. Particular mention may also be made of the treatment of radiation-induced emesis. Thus, the compounds of formula (I) may be used in the prevention of emesis induced by radiation therapy, e.g. irradiation of the thorax or abdomen, such as in the treatment of cancer; or in the treatment of radiation sickness.
The compounds of formula (I) do not possess dopamine antagonist activity and thus will not produce the undesirable side effects found with known anti-emetic agents such as metoclopramide.
It will be appreciated that the compounds of formula (I) may be used prophylactically and references in this specification to treatment include prophylactic treatment as well as the alleviation of acute symptoms.
A preferred class of compounds for use according to the invention is that represented by the formula (Ia): 
(wherein R1a represents a hydrogen atom or a methyl, ethyl, propyl, prop-2-yl, prop-2-enyl or cyclopentyl group; R3a represents a hydrogen atom; and either R2a represents a-methyl, ethyl, propyl or prop-2-yl group and R4a represents a hydrogen atom or R2a represents a hydrogen atom and R4a represents a methyl or ethyl group) and physiologically acceptable salts and solvates (e.g. hydrates) thereof.
Preferred compounds for use according to the present invention are:
1,2,3,9-tetrahydro-3-[(2-methyl-1H-imidazol-1-yl)methyl]-9-(prop-2-enyl)-4H-carbazol-4-one;
9-cyclopentyl-1,2,3,9-tetrahydro-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one; and
1,2,3,9-tetrahydro-3-[(2-methyl-1H-imidazol-1-yl)methyl]-9-(prop-2-yl)-4H-carbazol-4-one and their physiologically acceptable salts and solvates.
A particularly preferred compound is 1,2,3,9-tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one, and the physiologically acceptable salts and solvates (e.g. hydrates) thereof. A preferred form of this compound is the hydrochloride dihydrate.
The compounds of formula (Ia) are well absorbed from the gastro-intestinal tract. They do not prolong sleeping time in the pentobarbitone anaesthetised mouse indicating that there is no undesirable interaction with drug metabolising enzymes. Indeed they exhibit no effects on normal behaviour, are non-toxic and exhibit no undesirable effects in mice at doses up to 1 mg/kg intravenously.
Accordingly, the invention also provides a pharmaceutical composition which comprises at least one compound selected from 3-imidazolylmethyltetrahydrocarbazolone derivatives of the general formula (I), their physiologically acceptable salts and solvates, e.g. hydrates, for use in human or veterinary medicine, for the relief of nausea and vomiting and/or the promotion of gastric emptying e.g. for the relief of gastro-intestinal disorders associated with gastric stasis.
In a yet further aspect, the invention provides the use of a compound of formula (I) or a physiologically acceptable salt or solvate thereof, for the manufacture of a medicament for the relief of nausea and vomiting, and/or the promotion of gastric emptying e.g. for the relief of gastro-intestinal disorders associated with gastric stasis.
Pharmaceutical compositions for use in accordance with the present invention may be formulated in conventional manner using one or more physiologically acceptable carriers or excipients.
Thus the compounds of formula (I) and their physiologically acceptable salts and solvates may be formulated for oral, buccal, parenteral or rectal administration or in a form suitable for administration by inhalation or insufflation (either through the mouth or the nose).
For oral administration, the pharmaceutical compositions may take the form of, for example, tablets or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g. pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (e.g. lactose, microcrystalline cellulose or calcium hydrogen phosphate); lubricants (e.g. magnesium stearate, talc or silica); disintegrants (e.g. potato starch or sodium starch glycollate); or wetting agents (e.g. sodium lauryl sulphate). The tablets may be coated by methods well known in the art. Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents (e.g. sorbitol syrup, cellulose derivatives or hydrogenated edible fats); emulsifying agents (e.g. lecithin or acacia); non-aqueous vehicles (e.g. almond oil, oily esters, ethyl alcohol or fractionated vegetable oils); and preservatives (e.g. methyl or propyl-p-hydroxybenzoates or sorbic acid). The preparations may also contain buffer salts, flavouring, colouring and sweetening agents as appropriate.
Preparations for oral administration may be suitably formulated to give controlled release of the active compound.
For buccal administration the compositions may take the form of tablets or lozenges formulated in conventional manner.
The compounds of formula (I) may be formulated for parenteral administration by injection e.g. by bolus injection or continuous infusion. Formulations for injection may be presented in unit dosage form e.g. in ampoules or in multi-dose containers, with an added preservative. The compositions may take such forms as suspensions, solutions or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilising and/or dispersing agents. Alternatively, the active ingredient may be in powder form for constitution with a suitable vehicle, e.g. sterile pyrogen-free water, before use.
The compounds of formula (I) may also be formulated in rectal compositions such as suppositories or retention enemas, e.g. containing conventional suppository bases such as cocoa butter or other glycerides.
In addition to the formulations described previously, the compounds may also be formulated as a depot preparation. Such long acting formulations may be administered by implantation (for example subcutaneously or intramuscularly) or by intramuscular injection. Thus, for example, the compounds of formula (I) may be formulated with suitable polymeric or hydrophobic materials (for example as an emulsion in an acceptable oil) or ion exchange resins, or as sparingly soluble derivatives, for example, as a sparingly soluble salt.
For administration by inhalation the compounds for use according to the present invention are conveniently delivered in the form of an aerosol spray presentation from pressurised packs or a nebuliser, with the use of a suitable propellant, e.g. dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas. In the case of a pressurised aerosol the dosage unit may be determined by providing a valve to deliver a metered amount. Capsules and cartridges of e.g. gelatin for use in an inhaler or insufflator may be formulated containing a powder mix of a compound of formula (I) and a suitable powder base such as lactose or starch.
The compositions may, if desired, be presented in a pack or dispenser device which may contain one or more unit dosage forms containing the active ingredient. The pack may for example comprise metal or plastic foil, such as a blister pack. The pack or dispenser device may be accompanied by instructions for administration.
A proposed dose of the compounds of the invention for administration in man (of approximately 70 kg body weight) is 0.05 to 20 mg, preferably 0.1 to 10 mg of the active ingredient per unit dose which could be administered, for example, 1 to 4 times per day. The dose will depend on the route of administration and the body weight of the patient. It will be appreciated that it may be necessary to make routine variations to the dosage depending on the age and weight of the patient as well as the severity of the condition to be treated.
For oral administration a unit dose will preferably contain from 0.5 to 8 mg of the active ingredient. A unit dose for parenteral administration will preferably contain 0.1 to 8 mg of the active ingredient.
Aerosol formulations are preferably arranged so that each metered dose or xe2x80x98puffxe2x80x99 delivered from a pressurised aerosol contains 0.2 mg to 4 mg of a compound of the invention, and each dose administered via capsules and cartridges in an insufflator or an inhaler contains 0.2 to 20 mg of a compound of the invention. The overall daily dose by inhalation will be within the range 0.4 to 80 mg. Administration may be several times daily, for example from 2 to 8 times, giving for example 1, 2 or 3 doses each time.
The compounds of formula (I) may be administered in combination with other therapeutic agents, for example to aid absorption of the therapeutic agent where this is hindered by the patient""s condition, such as by gastric stasis associated with migraine. Thus, for example, the compounds may be administered in combination with antimigraine agents such as ergotamine, or antisecretory agents such as ranitidine. They may also be administered in combination with anticancer (e.g. cytostatic) drugs, for example to prevent nausea and vomiting associated with these agents. Cytostatic agents with which compounds of formula (I) may be administered include cyclophosphamide; alkylating agents; and platinum complexes such as cisplatin. Thus, a compound of formula (I) may be presented together with another therapeutic agent as a combined preparation for simultaneous, separate or sequential use, for the relief of nausea and vomiting, or gastrointestinal disorders associated with gastric stasis. Such a combined preparation may be, for example, a twin-pack. A preferred combination comprises a compound of formula (I) with a cytostatic agent, especially cisplatin.
In general, the presently available dosage forms of the known therapeutic agents will be suitable for use in such combined preparations. Thus, cisplatin may be provided in vials containing 10, 25 or 50 mg of the active ingredient.
The compounds of general formula (I) may be prepared by the process described in British patent application No. 2153821A.
Example 22 of British patent application 2153821 describes the preparation of a compound of formula (Ia) which is 3R-1,2,3,9-Tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one maleate.
A solution of the product from Example 7 (1,2,3,9-Tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]4H-carbazol-4-one) (0.5 g) was dissolved in hot methanol (30 ml) and treated with a hot solution of (xe2x88x92)di-p-toluoyl-L-tartaric acid monohydrate (0.7 g) in methanol (10 ml) and the resulting solution allowed to crystallise overnight to give the desired salt (0.8 g). This salt was dissolved in hot dimethylformamide (DMF, 20 ml), diluted with hot water (10 ml) and allowed to crystallise for 3 days. The product was filtered off, and dried in vacuo to give ca 95% enantiomerically pure (as shown by n.m.r.)(xe2x88x92)-di-p-toluoyl-L-tartaric salt (0.26 g) m.p. 170xc2x0-172xc2x0. A sample of the salt (0.2 g) was partitioned between 8% sodium bicarbonate (25 ml) and chloroform (2xc3x9725 ml). The combined extracts were dried and evaporated in vacuo to give pure free base (0.12 g). The base was dissolved in methanol (5 ml) acidified with maleic acid (0.045 g) and the salt precipitated by adding excess dry ether (80 ml) to give the title compound (0.08 g) m.p. 142-145xc2x0.
T.I.c. Silica, dichloromethane/ethanol/0.88 ammonia (100:8:1) Rf 0.3 detection u.v. and iodoplatinic acid, identical to the product from Example 7 (1,2,3,9-Tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one). The enantiomer ratio, determined by ""H n.m.r. was 95:5. A sample of the maleate salt showed no significant optical rotation in methanol. The free base, regenerated from the maleate salt, gave [xcex1]24D+16xc2x0 (c-0.34, MeOH). Analogous processes are also described in European patent application No. 86300423.
The efficacy of compounds of formula (I) in the promotion of gastric emptying and their anti-emetic activity have been demonstrated in standard animal models as described below.
(A) Gastric Emptying
Test compound: 1,2,3,9-tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one hydrochloride dihydrate. The effect of the test compound on gastric emptying was determined in guinea-pigs by following the progress of polystyrene-coated barium sulphate spheres (1 mm diameter) through the gut. The experimental method was based on that described by B. Costall et. al., Eur. J. Pharmacol 91, 197-205, 1983 and B. Cox et. al., Br. J. Pharmacol. 70, 104, 1980.
The spheres (approximatley 30 in number) were administered orally in 0.2 ml carboxymethylcellulose with 0.05 ml glycerine. At the same time, the test compound was administered intraperitoneally at doses of 0.001, 0.01 and 0.1 mg/kg. The control animals received saline, administered intraperitoneally, in place of the test compound. Passage of the spheres through the gut was monitored at 30-60 minute intervals over a period of 2 hours by X-ray location. The number of spheres leaving the stomach was recorded and expressed as a percentage of the total.
The results are given in Table 1 below
(B) Anti-Emesis
Test compound: 1,2,3,9-tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one hydrochloride dihydrate.
The effect of the test compound on emesis was demonstrated in ferrets according to the general method described by Florezyk, Schurig and Bradner (Cancer Treatment Report, 1982 66(1) 187-9) and summarised below. Both the test compound and cisplatin were prepared and administered in normal saline. The dose of test compound was calculated as the free base.
a) Controlxe2x80x94without Test Compound
Emesis was induced in groups of 6 male ferrets weighing between 1.5-2 kg, by intravenous administration of cisplatin at a dose of 10 mg/kg. The onset of emesis occurred between 38 and 75 minutes after injection and over a period of 2 hours the number of vomits/retches (episodes) was in the range 30-62 (average 42xc2x15 vomits/retches per 2 h). Behavioural changes characteristic of emesis were also noted.
b) With Test Compound
The test compound was administered to groups of 6 male ferrets (1.5-2 kg) by intravenous administration at doses of 0.01, 0.1 and 1 mg/kg, immediately prior to administration of cisplatin as described above. The animals were observed for 3 hours.
The results obtained are given in Table 2 below.
The effect of the test compound on emesis was also demonstrated following intraperitoneal administration, using a similar procedure to that described above.
Thus cisplatin was administered intraperitoneally to a group of 4 male ferrets at a dose of 9 mg/kg, and the time to onset of emesis and the number of emetic episodes were recorded. In a second group of four male ferrets the test compound was administered at a dose of 1 mg/kg i.p. 30 minutes before and 1 hour after intraperitoneal administration of cisplatin. The results are given in Table 3:
The following example illustrates the preparation of a compound of formula (I). Temperatures are in xc2x0C. Where indicated, solutions were dried over Na2SO4 and solids were dried in vacuo over P2O5 at 50xc2x0 overnight. Chromatography was carried out using the technique described by W. C. Still et al (J. Org. Chem., 1978, 43, 2923-2925), on kieselgel 9385.